The existence of inhibin as a water-soluble substance of gonadal origin which acts specifically at the pituitary level to suppress the secretion of follicle-stimulating hormone (FSH) was postulated by McCullagh more than 50 years ago, Science, 76, 19-20 (1932). There has been great interest in it, and many laboratories have attempted to isolate and characterize such a substance.
The publications of a group working at the University of Melbourne in Australia (H. W. G. Baker et al., Adv. Bioscience, 1982, p. 123-132, and Annals N.Y. Academy of Sciences. 383 1982, pp. 329-342), reported on the disagreement between investigators as to the size of the inhibin molecule and as to what methods should be used for its attempted purification; moreover, the discussions reported at the end of these articles point out that there was even disagreement between investigators as to whether there was a hormone which fit the proposed definition of inhibin because bioassays that were being used in hopes of isolating such a substance were capable of measuring the activities of different substances that could have a similar effect. Thus, in 1982, investigators were generally admitting that methods for satisfactorily purifying a substance that appeared to have the activity of the proposed "inhibin" molecule had simply not yet been developed and, as a result, that the isolates that were then being obtained were still heterogeneous.
In P.N.A.S., 82, 7217-7221 (November 1985), Ling et al. published the N-terminal sequences of a heterodimer of about 32 kD having inhibin activity that had been isolated from porcine follicular fluid. In Nature, 318, 659-663, (1985) Mason et al. published sequences for the subunits of porcine inhibin deduced from studies of cDNA, showing an .alpha.-chain of 134 residues linked to a .beta.-chain of either 115 or 116 residues. In B.B.R.C., 135, 3, 957-964 (Mar. 28, 1986), Mason et al. published sequences for the subunits of human inhibin similarly deduced from cDNA, also showing an .alpha.-chain of 134 residues linked to a .beta.-chain of 115 or 116 residues. In May, 1986, in P.N.A.S., 83, 3091-3095, Foragi et al. published sequences for subunits of bovine inhibin deduced from analysis of cDNA.
Inhibin may be used to regulate fertility, gonadotropin secretion or sex hormone production in mammalians, in females and particularly in males.